Re: [PATCH v5 10/15] x86/purgatory: Disable CFI

Kees Cook
2021-10-13T19:06:00Z

On Wed, Oct 13, 2021 at 11:16:53AM -0700, Sami Tolvanen wrote:
> Disable CONFIG_CFI_CLANG for the stand-alone purgatory.ro.

If there's a v6, this commit log might do well to have a "why" added. I
assume it'd be something like:

... because purgatory is not running with a full kernel mapping with
jump tables, etc...

Reviewed-by: Kees Cook <keescook@chromium.org>

>
> Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> Tested-by: Nick Desaulniers <ndesaulniers@google.com>
> Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
> ---
> arch/x86/purgatory/Makefile | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/arch/x86/purgatory/Makefile b/arch/x86/purgatory/Makefile
> index 95ea17a9d20c..911954fec31c 100644
> --- a/arch/x86/purgatory/Makefile
> +++ b/arch/x86/purgatory/Makefile
> @@ -55,6 +55,10 @@ ifdef CONFIG_RETPOLINE
> PURGATORY_CFLAGS_REMOVE += $(RETPOLINE_CFLAGS)
> endif
>
> +ifdef CONFIG_CFI_CLANG
> +PURGATORY_CFLAGS_REMOVE += $(CC_FLAGS_CFI)
> +endif
> +
> CFLAGS_REMOVE_purgatory.o += $(PURGATORY_CFLAGS_REMOVE)
> CFLAGS_purgatory.o += $(PURGATORY_CFLAGS)
>
> --
> 2.33.0.1079.g6e70778dc9-goog
>

--
Kees Cook